In preliminary processing of information there exists a type of problems to estimate against a noise background, a steady-state value with a final result to be represented in a digital form.
A problem of such a type exist in measuring temperature of molten metal, for example steel, by means of a temperature sensor which is immersed in the melt for a short period of time, when it is required to determine in a digital form the signal value received from the sensor, which is set after termination of a transient process caused by the drift of temperature sensors.
Known in the art is a digital computing device designed for checking parameters of a molten metal. (See British Accepted Application No. 1477564). The above device can be employed for determining in a digital form a steady-state value of the analogue signal, for example, for determining a molten metal temperature measured by means of an immersion thermocouple.
Said device comprises an analogue-to-digital converter for converting an analogue signal into a numerical pulse code, having an output of code pulses corresponding to a positive increment of the analogue signal and an output of code pulses corresponding to a negative increment of the analogue signal, a clock pulse generator, a synchronization unit for distribution in time of code and clock pulses, connected with the inputs and outputs of the analogue-to-digital converter and to an output of the clock pulse generator. For determining local increments of the analogue signal there are provided a first and a second threshold counter, the digit outputs of which are connected to inputs of decoders of the zero state of threshold counters, outputs of said decoders being connected to subtract count blocking inputs of the respective threshold counters. The device also comprises a time interval discriminator designed for selecting time intervals between sequence instants of time when a local increment of the analogue signal assumes a predetermined value. Initial setting inputs of the time interval discriminator are connected to overflow outputs of said threshold counters. An output of synchronized clock pulses of the synchronization unit is electrically connected to a count input of the time interval discriminator. Synchronized code pulse outputs of the synchronization unit are electrically connected to the threshold counters and to a reversible counter designed for generating a parallel code of the result. A register connected with its information input to digit outputs of the reversible counter, and with its control input to the output of the time interval discriminator provides for a storage of the computed result which is displayed in a digital form in a digital display unit.
During the process of determining temperature of molten metal, in the reversible counter there is formed a code proportional to the current readings of the analogue signal received from the temperature sensor. If positive or negative increments of the signal exceeds a predetermined threshold .SIGMA..sub.o of non-sensitivity to the signal deviations from its steady-state value, caused by interference effect, there appear pulses at the overflow outputs of the threshold counters. Each such pulse sets into the initial state the time interval discriminator which counts up a number of synchronized clock pulses. If within a predetermined time interval .tau..sub.o set with the aid of the time interval discriminator, an increment of the signal does not exceed the predetermined threshold .SIGMA..sub.o, there appears a signal at the output of the time interval discriminator, which indicates that the analogue signal has assumed its steady-state value. The parallel code contained in this instant of time in the reversible counter enables said ready-state value of the analogue signal to be estimated. The signal, which is fed to the control input of the register from the output of the time interval discriminator, contains information indicative of the steady-state value of the analogue signal.
It should be noted that the parallel code fed to the register may vary from the code of the steady-state value of the analogue signal by a value of .+-.0.5 .SIGMA..sub.o. Thus, the maximum error in determining a steady-state value of the analogue signal with the aid of the above device cannot be less than 0.5 .SIGMA..sub.o.
With the increase of the noise level the non-sensitivity threshold .SIGMA..sub.o has to be increased, which brings about an increase in the maximum error in determining the ready-state value of the analogue signal. Thus, an accuracy in determining the steady-state value of the analogue signal by means of the above device considerably depends on the noise level.
For example, when determining molten steel temperature is done by means of the existing temperature sensors, which are dipped in the melt for a short period of time, the noise level may be equivalent to the deviation of the analogue signal value in the order of 10.degree. C. This being the case, the threshold .SIGMA..sub.o of non-sensitivity has to be equal to 10.degree. C. which may cause an error in determining molten steel temperature within .+-.5.degree. C. In smelting and casting a high-quality steel such an error in determining its temperature is not permissible.